Region-Specific Sourcing of Lignocellulose Residues as Renewable Feedstocks for a Net-Zero Chemical Industry.

Biobased chemicals, crucial for the net-zero chemical industry, rely on lignocellulose residues as a major feedstock. However, its availability and environmental impacts vary greatly across regions. By 2050, we estimate that 3.0-5.2 Gt of these residues will be available from the global forest and agricultural sectors, with key contributions from Brazil, China, India, and the United States. This supply satisfies the growing global feedstock demands for plastics when used efficiently. Forest residues have 84% lower climate change impacts than agricultural residues on average globally but double the land-use-related biodiversity loss. Biobased plastics may reduce climate change impacts relative to fossil-based alternatives but are insufficient to fulfill net-zero targets. In addition, they pose greater challenges in terms of biodiversity loss and water stress. Avoiding feedstock sourcing from biodiversity-rich areas could halve lignocellulose residues-related biodiversity loss without significantly compromising availability. Improvements in region-specific feedstock sourcing, agricultural management and biomass utilization technologies are warranted for transitioning toward a sustainable chemical industry.

Economic and Environmental Competitiveness of Ethane-Based Technologies for Vinyl Chloride Synthesis.

The synthesis of the vinyl chloride monomer (VCM), employed to manufacture poly(vinyl chloride) (PVC) plastic, primarily relies on oil-derived ethylene, resulting in high costs and carbon footprint. Natural gas-derived ethane in VCM synthesis has long been considered a transformative feedstock to lower emissions and expenses. In this work, we evaluate the environmental potential and economics of recently developed catalytic ethane chlorination technologies for VCM synthesis. We consider the ethylene-based business-as-usual (BAU) route and two different ethane-based processes evaluated at their current development level and their full potential, i.e., ideal conversion and selectivity. All routes are assessed under two temporal scenarios: present (2020) and prospective (2050). Combining process simulation and life cycle assessment (LCA), we find that catalytic ethane chlorination technologies can lower the production cost by 32% at their current development state and by 56% when considering their full potential. Though environmentally disadvantageous in the 2020 scenario, they emerge as more sustainable alternatives to the BAU in the 2050 scenario, reducing the carbon footprint of VCM synthesis by up to 26% at their current state and up to 58% at their full potential. Going beyond VCM synthesis, our results highlight prospective LCA as a powerful tool for assessing the true environmental implications of emerging technologies under more decarbonized future energy scenarios.

Reaction-Induced Formation of Stable Mononuclear Cu(I)Cl Species on Carbon for Low-Footprint Vinyl Chloride Production.

Copper catalysts are attractive candidates for Hg-free vinyl chloride monomer (VCM) production via acetylene hydrochlorination due to their non-toxic nature and high stability. However, the optimal architecture for Cu-based catalysts at the nanoscale is not yet fully understood. To address this gap, the metal precursor and the annealing temperature are modified to prepare copper nanoparticles or single atoms, either in chlorinated or ligand-free form, on an unmodified carbon support. Evaluation in the reaction reveals a remarkable convergence of the performance of all materials to the stable VCM productivity of the single-atom catalyst. In-depth characterization by advanced microscopy, quasi in situ and operando spectroscopy, and simulations uncover a reaction-induced formation of low-valent, single atom Cu(I)Cl site motif, regardless of the initial nanostructure. Various surface oxygen groups promote nanoparticle redispersion by stabilizing single-atom CuClx species. The anchoring site structure does not strongly influence the acetylene adsorption energy or the crucial role they play in stabilizing key reaction intermediates. A life-cycle assessment demonstrates the potential environmental benefits of copper catalysts over state-of-the-art alternatives. This work contributes to a better understanding of optimal metal speciation and highlights the sustainability of Cu-based catalysts for VCM production.

Economic and Environmental Barriers of CO2-Based Fischer-Tropsch Electro-Diesel.

Electro-fuels are seen as a promising alternative to curb carbon emissions in the transport sector due to their appealing properties, similar to those of their fossil counterparts, allowing them to use current infrastructure and state-of-the-art automotive technologies. However, their broad implications beyond climate change remain unclear as previous studies mainly focused on analyzing their carbon footprint. To fill this gap, here, we evaluated the environmental and economic impact of Fischer-Tropsch electro-diesel (FT e-diesel) synthesized from electrolytic H2 and captured CO2. We consider various power (wind, solar, nuclear, or the current mix) and carbon sources (capture from the air (DAC) or a coal power plant) while covering a range of impacts on human health, ecosystems, and resources. Applying process simulation and life cycle assessment (LCA), we found that producing e-diesel from wind and nuclear H2 combined with DAC CO2 could reduce the carbon footprint relative to fossil diesel, leading to burden-shifting in human health and ecosystems. Also, it would incur prohibitive costs, even when considering externalities (i.e., indirect costs of environmental impacts). Overall, this work highlights the need to embrace environmental impacts beyond climate change in the analysis of alternative fuels and raises concerns about the environmental appeal of electro-fuels.

Navigating within the Safe Operating Space with Carbon Capture On-Board.

Despite the global pandemic that recently affected human and cargo transportation, the emissions of the maritime sector are projected to keep growing steadily. The International Maritime Organization focused on boosting the fleets' efficiency to improve their environmental performance, while more sustainable fuels are currently under investigation. Here, we assess the economic, technical, and environmental feasibility of an interim solution for low-carbon shipping using state-of-the-art CO2 capture technology, namely, chemical absorption, on-board cargo ships. We compute the carbon footprint of this alternative and perform an absolute sustainability study based on seven planetary boundaries. Our results show that the capture on-board scenario can achieve 94% efficiency on the net CO2 emissions at 85 $/tCO2 while substantially reducing impacts on core planetary boundaries (relative to the business as usual) and outperforming a direct air capture scenario in global warming and all planetary boundaries, except for the nitrogen flow. Hence, capture on-board seems an appealing solution to decarbonize shipping in the short term while alternative carbon-free fuels and related infrastructure are developed and deployed.